Design of a Commercial Hybrid VTOL UAV System

For the last four decades Unmanned Air Vehicles (UAVs) have been extensively used for military operations that include tracking, surveillance, active engagement with weapons and airborne data acquisition. UAVs are also in demand commercially due to their advantages in comparison to manned vehicles. These advantages include lower manufacturing and operating costs, flexibility in configuration depending on customer request and not risking the pilot on demanding missions. Even though civilian UAVs currently constitute 3 % of the UAV market, it is estimated that their numbers will reach up to 10 % of the UAV market within the next 5 years. Most of the civilian UAV applications require UAVs that are capable of doing a wide range of different and complementary operations within a composite mission. These operations include taking off and landing from limited runway space, while traversing the operation region in considerable cruise speed for mobile tracking applications. This is in addition to being able traverse in low cruise speeds or being able to hover for stationary measurement and tracking. All of these complementary and but different operational capabilities point to a hybrid unmanned vehicle concept, namely the Vertical Take-Off and Landing (VTOL) UAVs. In addition, the desired UAV system needs to be cost-efficient while providing easy payload conversion for different civilian applications. In this paper, we review the preliminary design process of such a capable civilian UAV system, namely the TURAC VTOL UAV. TURAC UAV is aimed to have both vertical take-off and landing and Conventional Take-off and Landing (CTOL) capability. TURAC interchangeable payload pod and detachable wing (with potential different size variants) provides capability to perform different mission types, including long endurance and high cruise speed operations. In addition, the TURAC concept is to have two different variants. The TURAC A variant is an eco-friendly and low-noise fully electrical platform which includes 2 tilt electric motors in the front, and a fixed electric motor and ducted fan in the rear, where as the TURAC B variant is envisioned to use high energy density fuel cells for extended hovering time. In this paper, we provide the TURAC UAV’s iterative design and trade-off studies which also include detailed aerodynamic and structural configuration analysis. For the aerodynamic analysis, an in-house software including graphical user interface has been developed to calculate the aerodynamic forces and moments by using the Vortex Lattice Method (VLM). Computational Fluid Dynamics (CFD) studies are performed to determine the aerodynamic effects for various configurations For structural analysis, a Finite Element Model (FEM) of the TURAC has been prepared and its modal analysis is carried out. Maximum displacements and maximal principal stresses are calculated and used for streamlining a weight efficient fuselage design. Prototypes have been built to show success of the design at both hover and forward flight regime. In this paper, we also provide the flight management and autopilot architecture of the TURAC. The testing of the controller performance has been initiated with the prototype of TURAC. Current work focuses on the building of the full fight test prototype of the TURAC UAV and aerodynamic modeling of the transition flight.     

Synthesis and characterization of nanolamellar tungsten and molybdenum disulfides

Tungsten and molybdenum disulfides were produced in direct self-sustained combustion in argon between elementary sulfur and metal (W, Mo) nanopowders prepared by electrical explosion of wires. The results of XRD analysis show that the main phases of the synthesized nanopowders are hexagonal WS₂ and MoS₂. According to SEM and TEM observations, they are agglomerated nanolamellar particles of thickness 40–150 nm and width 100–3000 nm.     

Electrical and Magnetic Transport Properties of Nanocrystalline Fe73.5Si13.5B9Cu1Nb3 Alloy

Electrical and magnetic transport properties of Fe_73.5Si_13.5B₉Cu₁Nb₃ (FINEMET) metallic ribbons prepared by standard melt-spinning technique have been investigated through dc and ac magnetic as well as electrical properties. Fe_73.5Si_13.5B₉Cu₁Nb₃ shows conventional anisotropic magnetoresistance (MR) which is found to vary from 1 to 15 %. The dynamic behaviour of the sample vibrating at a constant frequency with the help of an external transducer in an external magnetic field is investigated. It is observed that a small self-induced ac voltage is superimposed on the dc response of the sample. This small ac signal is observed to be periodic in nature and may be attributed to the presence of non-magnetic metallic species in the ribbon. The effect of temperature (ranging from 30 to 550 °C) on the resistivity of the sample is measured and the glass transition temperature (T _g) of the alloy is estimated from the dc resistivity anomaly observed at the elevated temperature. The frequency dependent responses of permeability, quality factor and dissipation factor are studied by Wayne Kerr impedance analyser with frequency range of 100 Hz–100 MHz. The observed electrical and magnetic properties of the material indicate that the alloy in its ribbon form is suitable for its potential use in electrical and magnetic switching devices.     

Post‐Disaster least loaded lightpath routing in elastic optical networks

Disaster events directly affect the physical topology of core networks and may lead to simultaneous failure of multiple lightpaths leading to massive service outages for network operators. To recover from such a failure scenario, the existing routing algorithms running on network nodes (routers or switches) typically attempt to reestablish the connections over new routes with shortest distances and hop count approach. However, this approach may result in congestion on some links, while other links may have the unutilized capacity. Hence, intelligent lightpath computing techniques are required to efficiently route network traffic over the new routes by considering traffic load of each link in addition to distance and hop count to minimize network congestion. In this paper, we have proposed a capacity‐constrained maximally spatial disjoint lightpath algorithm to tackle the provisioning and restoration of disrupted lightpaths in a postdisaster scenario in the context of elastic optical networking. This algorithm computes an alternate least loaded lightpath for disrupted primary lightpath using capacity‐constrained shortest lightpath. Alternate lightpath selection is based on a criteria parameter for a lightpath to be least loaded and constrained by either the length or the spatial distance between primary and alternate lightpaths. The spatial distance between lightpaths enables to reestablish the disrupted connection request away from disaster proximity. The performance of the proposed algorithm is evaluated through simulation for several parameters like blocking probability, network utilization, connection success rates, and minimum spatial distance.     

Grain Refinement through Shear Banding in Severely Plastic Deformed A206 Aluminum Alloy

The present work is conducted to study the microstructure and texture evolutions in an as‐cast A206 aluminum alloy after applying severe plastic deformation. Toward this end, the material is severely deformed through accumulative back extrusion (ABE) technique at 200 °C and followed by assessing the room temperature mechanical properties of the products. The macro shear‐bands formation in the highly strained regions can result in grain refinement through the geometric dynamic recrystallization mechanism. A significant refinement is also characterized within the micro shear‐bands; this is attributed to the intensified substructure development and the occurrence of continuous dynamic recrystallization. The corresponding inverse pole figure maps show similar orientation for these newly refined grains with the parent ones. A random texture is produced through sub‐grain rotation to dissimilar orientation at the intersection of micro‐bands. The assessment of mechanical properties of the processed materials reveal significant increase in both yield and ultimate tensile strength values. The hardness profiles also demonstrate a relatively homogenous microstructure after three and five ABE passes holding a mean hardness value of 183 Vickers.     

On spatially disjoint lightpaths in optical networks

Within the communication networks, a delayed constrained data packet is the one that will be dropped if not being served before a certain deadline time, which causes data packet loss affecting the quality of service (QoS). In this paper, we study the blocking probability and the mean delay of such delay constrained packets in an asynchronous single-wavelength optical buffer in optical packet switching networks, where the packet arrival process follows the Poisson process and the packet-length distribution is assumed to be general. We obtain the integral equations of the modeled system and the exact expressions of blocking probabilities and the mean delays. Numerical examples are provided to validate the results with interesting observations being highlighted.     

Network Performance Improvement of All-Optical Networks Through an Algorithmic Based Dispersion Management Technique

Network blocking performance due to wavelength continuity constraint in a well-connected all-optical network can be efficiently reduced by utilizing wavelength converters. Nevertheless, the introduction of high bit rate optical services with strict tolerance to signal quality would have a serious impact on the overall network performance since in this circumstance, a request can be blocked due to unacceptable signal quality of potential routes. Chromatic dispersion tolerance, for example, is reduced by the square of the bit rate. By extending the typical application of parametric wavelength converter in solving a wavelength continuity problem, this paper aims to enhance chromatic dispersion management through an improved wavelength conversion algorithm. Consequently, significant improvement in network performance has been demonstrated through reduction in the dispersion effect when the proposed engineering rule is included in the conversion process.     

Tensile Properties and Work Hardening Behavior of Laser-Welded Dual-Phase Steel Joints

The aim of this investigation was to evaluate the microstructural change after laser welding and its effect on the tensile properties and strain hardening behavior of DP600 and DP980 dual-phase steels. Laser welding led to the formation of martensite and significant hardness rise in the fusion zone because of the fast cooling, but the presence of a soft zone in the heat-affected zone was caused by partial vanishing and tempering of the pre-existing martensite. The extent of softening was much larger in the DP980-welded joints than in the DP600-welded joints. Despite the reduction in ductility, the ultimate tensile strength (UTS) remained almost unchanged, and the yield strength (YS) indeed increased stemming from the appearance of yield point phenomena after welding in the DP600 steel. The DP980-welded joints showed lower YS and UTS than the base metal owing to the appearance of severe soft zone. The YS, UTS, and strain hardening exponent increased slightly with increasing strain rate. While the base metals had multi-stage strain hardening, the welded joints showed only stage III hardening. All the welded joints failed in the soft zone, and the fracture surfaces exhibited characteristic dimple fracture.     

Fine needle aspiration biopsy of salivary gland, 1985-1995

Cellular insulin resistance in polycystic ovary syndrome (PCOS) has been shown to involve a novel postbinding defect in insulin signal transduction. To find possible mechanisms for this defect, adipocytes were isolated from age- and weight-matched obese normal cycling (NC) and PCOS subjects. Insulin sensitivity for glucose transport stimulation was impaired in PCOS adipocytes (EC50 = 290 +/- 42 pmol/L) compared to that in NC cells (93 +/- 14; P < 0.005). The lipolytic responses to isoproterenol as well as maximal suppression by insulin were similar in NC and PCOS adipocytes. However, PCOS cells were less sensitive to the antilipolytic effect of insulin (EC50 = 115 +/- 33 pmol/L) compared to NC cells (42 +/- 8; P < 0.01). Treatment of adipocytes from NC subjects with the adenosine receptor agonist N6-phenylisopropyl adenosine had no effect on either insulin responsiveness or sensitivity for glucose transport stimulation. However, N6-phenylisopropyl adenosine treatment was able to normalize insulin sensitivity in PCOS cells (EC50 = 285 +/- 47 vs. 70 +/- 15 pmol/L, before and after treatment; P < 0.05). In conclusion, our results suggest that insulin resistance in PCOS, as accessed in the adipocyte, occurs at an early step in insulin signaling that is common for glucose transport and lipolysis. In addition, this insulin resistance involves an impairment of the system by which adenosine acts to modulate insulin signal transduction.     

The enhanced humidity sensing performance of calixarene/PMMA hybrid layers: QCM sensing mechanism

Journal of Materials Science: Materials in Electronics - This paper describes the preparation of the calix-4/PMMA hybrid QCM sensor by electrospinning of calix[4]arene derivative having carboxylic...